JPS6056676B2 - concrete composite panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concrete composite panel;
The purpose is to propose a concrete composite panel with large load-bearing capacity and deformation capacity.

As shown in FIG. 1, the concrete composite panel has a plurality of girder webs 2 between a pair of opposing steel plates 1, and a concrete layer 4, which is prevented from slipping by a slip prevention material 3, is placed between the pair of steel plates 1. Have it in a sandwich form. In the known composite panel, the concrete layer 4 consists of plain concrete, ie concrete mixed with gravel and having a sufficiently high strength and a suitable coarseness. The structural features of such a composite panel include: 1. Since it has a relatively large self-weight, when used as a structural material for a large offshore structure, it can exert a ballast effect to offset buoyancy.

2. Has great deformation ability and can absorb a large amount of energy before collapsing.

3. Since steel plates are placed on the outside, waterproof performance will not be impaired even if cracks occur in the internal concrete layer.

4. Block joint work is highly reliable because it mainly involves welding.

etc. are listed.

In order to investigate the strength characteristics of this composite panel, the inventors fabricated a millimeter model of unit width and conducted a loading test.

FIG. 2 shows a case where the scallop model 5 is subjected to a combined bending and shearing load.

Arrow 7 indicates the load direction. The crack occurrence situation in this case is shown in FIG. As is clear from Fig. 4, cracks X occur from the rubbing position of the concrete layer 8,
An arch was formed by progressing toward the diagonal 450, and a high load was borne. When the load further increased, collapse occurred, buckling of the compression side steel plate 9A, and crushing of a part of the concrete layer 8 10. This occurred due to the fracture of the tension side steel plate 9B.From the above, the sandwich type composite structure ultimately bears a high load due to the arch effect, and the deformation capacity increases due to the large deformation of the tension side steel plate. FIG. 3 shows a case where the scallop model 11 is mainly subjected to shearing load.

Arrow 13 indicates the load direction. The occurrence of cracks in this case is shown in FIG. When a load is applied, a crack Y occurs near the shearing position, and due to the shearing effect, the crack Y
Progress to 50. As a result, an arch is formed in the rope model 11, which bears the load up to the high load area. When the load further increased, a crack Z suddenly occurred in the concrete layer 14 due to the diagonal tension caused by shearing, the concrete layer 14 was crushed, and the rice cake model 11 collapsed. The deformation capacity until cal collapse is sufficiently large, and the amount of absorption energy is large. Figure 2~
Concrete layer 8 of beam model 5, 11 explained in FIG.
No. 14 uses the above-mentioned ordinary concrete.
When mortar (concrete without gravel) or low-strength concrete was used instead of ordinary concrete, the failure of the beam model was as follows. When a load is applied, a crack corresponding to crack Y occurs, but at a low load a crack corresponding to crack Z occurs, and the beam model suddenly breaks. In other words, the beam type failed due to diagonal tension due to shearing without forming an arch.
There was almost no deformation ability, and the concrete layer did not collapse. The difference in the crack occurrence situation between the former and the latter can be considered as follows.

1 As shown in Fig. 6, aggregate (
When there is an appropriate amount of aggregate 16 (gravel) 16, that is, when the coarse grain ratio is good, even if a crack corresponding to the crack Y occurs, there is an interlocking effect between the aggregates 16 on the crack surface 17, and the crack surface 17 However, it also transmits some shear force.

2 As shown in Fig. 7, even if a micro-crack B occurs at the outpost of the crack corresponding to the crack Z due to diagonal tension, the aggregate 16 acts as a crack arrester, hindering its progress and development. It will be done.

3 Even if the concrete contains aggregate 16, if its strength is low, the tensile strength and the adhesion between the aggregate 16 and cement will naturally decrease, so the effect of 12 above is natural! descend.

The final failure of the beam model under shear load is due to the crack Z1, that is, the diagonal tension crack.

Therefore, when steel fiber is mixed into concrete, the tensile strength of concrete is improved! It is presumed that this diagonal tension cracking can be resisted and the shear strength can be increased. In fact, the tensile strength of concrete with such steel fibers is improved by 40-50%. Figure 8 shows the load-deflection relationship with and without steel fibers mixed in. In the figure, the solid line A shows the characteristics of ordinary concrete, the broken line shows the characteristics of steel fiber concrete, and Pl and P2 show the respective collapse points. From this figure, it can be seen that when 1.5% by volume of steel fiber is mixed, the final strength increases by 22% and the rigidity approximately doubles. Therefore, steel fiber concrete can be said to be an extremely excellent structural material, but its deformability is reduced to about 20% compared to ordinary concrete. As shown by the solid line, in the case of the beam model using steel fiber concrete, a crack corresponding to the crack Y occurred, but the width of the crack was small. Then, a crack corresponding to crack Z suddenly appeared, and the beam model collapsed. Furthermore, the elongation of the steel plate on the tension side was small, so almost no deflection occurred. The reason for this is thought to be as follows. Although the tensile strength of concrete is greatly increased by the steel fibers, on the other hand, cracks corresponding to the above-mentioned crack Y are restrained because the ratio of steel to concrete increases.

Therefore, energy absorption due to the interlocking effect of the aggregate at the crack Y position is eliminated. 2 Since the crack corresponding to the crack Y is restrained, the elongation deformation of the tension side steel plate is restrained.

3. Since the crack corresponding to the crack Y does not develop sufficiently, an arch is not formed and a large shear deformation, that is, diagonal tension occurs in the internal concrete.

From the above, it can be seen that the following points should be kept in mind in order to obtain a structure with excellent load carrying capacity and large deformability.

1. To withstand high loads, form an arch and increase its arch tensile strength (to resist diagonal tension cracking).

). 2. In order to enhance the deformation ability, it is necessary to generate cracks corresponding to the crack Y described above.

3. Since the aggregate interlocking effect of the crack surface of the crack corresponding to the crack Y is useful for energy absorption, this interlocking mechanism must be taken into consideration.

The present invention has been made with the above points 1 to 3 in mind, and examples thereof will be described below with reference to FIGS. 9 to 11.

A concrete composite panel is shown in Figure 9.

20A and 20B are steel plates having stoppers 20a and 20b, respectively, and a plurality of girder webs 21A and 21B are interposed vertically and horizontally in a grid pattern between the pair of steel plates 20A and 20B.

A concrete layer 22 is constructed in one section surrounded by these girder webs 21A and 21B. The concrete layer 22 consists of a normal concrete layer 22A and a steel fiber concrete layer 22B, and the steel fiber concrete layer 22B is formed in a spherical shape at the center of the section, while the normal concrete layer 22A is formed around it. And anti-scratch materials 20a, 20
It is prevented from slipping by b. Such concrete composite panels can bear high loads in three dimensions.
In other words, steel fiber concrete, which has twice the tensile strength of ordinary concrete, is placed in the latch where diagonal tension cracks are expected to occur under three-dimensional loads, so that diagonal tension cracks will not occur. mosquito,
Or be restrained. Therefore, sudden destruction does not occur,
It has great deformation ability. Next, the manufacturing method will be explained.

First, a steel fiber concrete ball 23 made into a spherical shape in advance is placed in the center of each section. At this time, as clearly shown in FIG. 10, a spacer rod 24 is implanted in the ball 23, and the spacer rod 24 secures the distance between the steel plates 20A, 20B and the girder webs 21A, 21B. Next, ordinary concrete is poured through the hole 25 in the center of the garter web 21B and allowed to harden. As is clear from the above explanation,
The present invention can easily provide a concrete composite panel with excellent load-bearing capacity and deformability.

[Brief explanation of drawings]

Figure 1 is a broken perspective view of a conventional example, Figures 2 and 3 are perspective views of a beam model, Figures 4 and 5 are illustrations of crack occurrence,
Figures 6 and 7 are explanatory diagrams of the meshing effect, Figure 8 is a load-deflection relationship diagram, Figures 9 and 10 are examples of the present invention, and Figure 9 is a cutaway perspective view. FIG. 10 is a perspective view of the ball 23. 20A, 20B... Steel plate, 21A, 21B... No guard web, 22... Concrete layer, 22
A... Ordinary concrete layer, 22B...
-Steel fiber concrete layer.

Claims (1)

[Claims] 1. A concrete composite panel characterized by having a spherical steel fiber concrete layer and a surrounding ordinary concrete layer between a pair of opposing steel plates.